(i) Field of the Invention
The present invention relates in general to cushioning devices, and particularly to a combination mattress comprised of an air cell mattress and a spring mattress. The air cell mattress provides a uniform supporting force and the spring mattress provides deformation of the sleeping surface for comfort. Additionally, the air pressure of the air cell mattress is adjustable for added comfort.
(ii) Description of the Related Art
Various attempts have been made over the years to create a mattress that provides the utmost comfort and therapeutic care for a user. These attempts include the use of springs or air cells as key components of the mattress. Traditional mattresses are made from a combination of springs and padding encased in or surrounded by some form of cover. Mattresses have also been comprised of a plurality of air cells or air pockets surrounded by some type of cover that is typically padded.
The traditional spring mattress is typically comprised of a plurality of coil springs arranged in a rectangular pattern. The coil springs are encased within a padded cover and form a continuous surface upon which a person may rest. Spring mattresses support a person by the individual springs compressing proportionally to the force being exerted by the user on that spring. When compressed, the springs will exert an upward or supporting force on the user proportionate to the compression. When a user is on a spring mattress, the heavier portions of the user's body will exert a greater force on the springs supporting that portion of the body thereby causing a greater compression of the springs at those locations. Therefore, a user lying on a spring mattress will experience a larger pressure or supporting force below the heavier parts of their body as opposed to the supporting forces being experienced on the lighter portions of their body. This results in an uneven weight distribution on the spring mattress and concentrations of greater force along the user's body beneath the heavier portions of the user than beneath the lighter portions of the user.
The differential pressure experienced along a user's body is a drawback to conventional spring mattresses. If a user were to be required to be in a recumbent position on a conventional spring mattress for an extended period of time such concentrations of force and pressure would decrease the blood flow in the capillaries of that portion of the body and result in discomfort, soreness, or possibly bed sores. Additionally, because a user's weight is not evenly distributed over the spring mattress, certain sections of the spring mattress and the springs below these sections will repeatedly experience significantly larger compressions than other areas of the spring mattress and subsequently wear out sooner and thus limit the useful life of the mattress.
Air mattresses have been utilized to avoid the concentration of supporting forces on a user's body that are caused by spring mattresses. Typical air mattresses are comprised of a plurality of air cells. The air cells contain a fixed volume of air and when a user lies on an air mattress, the air pressure in the individual air cells will increase in proportion to the weight of the user being supported by the air cell and be distributed evenly throughout the air cell. Therefore, a user would experience a uniform supporting force over the surface of the air cell on which they are lying. Depending upon the size of the air cell, the pressure could be distributed over a large area of a user's body or concentrated on a small area like with a spring mattress.
Some air mattresses allow the user to adjust the amount of air within the air mattress. Typically, this type of mattress allows the user to add air to or remove air from the air cells of the air mattress either manually or with the use of an air pump. The custom adjusting of the air pressure within the air mattress allows the user to adjust the air mattress to achieve personalized comfort.
Some air mattresses divide the plurality of air cells up into zones. In this type of air mattress, all of the air cells within a zone are interconnected so that the air within the air cells freely moves between the air cells within that zone. The air cells within a zone, therefore, are at a uniform pressure and the supporting force experienced by a user's body is evenly distributed throughout the zone and the problem of concentrations of pressure on a user's body is avoided.
When an air mattress is divided into zones, the zones are typically independent of one another and do not communicate. The different zones will be positioned within the mattress to support different portions of a user's body, such as the head/shoulder area, the hip/torso area, or the feet/lower leg area. Because the zones are independent, they can be inflated to different pressures. Therefore, each zone can be custom inflated to provide user specific levels of comfort. A user can inflate any zone that supports a heavier part of the body to a higher pressure. Therefore, when the heavier part of the body is lying on that zone, the user will experience less deformation of the air cells within that zone as the weight of the body is evenly distributed throughout the zone. By inflating the zones of the air mattress to differing pressures, the user can alter the amount of deformation of the various zones.
However, the air cells of an air mattress have a maximum volume determined by their dimensions. Because the air cells have a maximum volume, the amount of deformation of the air mattress when supporting a user is limited by the amount of air pressure within the air cells, the number of air cells in communication, and the limited elasticity of the air cell walls. The larger the number of independent air cells within an air mattress the greater the variety of deformations and resulting comfort that can be experienced by a user and the closer the air mattress approximates a spring mattress. However, as the number of independent air cells within an air mattress increases, the ability to distribute the supporting forces over a large area of the user is diminished. Additionally, as the number of independent air cells increases the complexity and difficulty in providing individual control of the air pressure in the independent air cells increases thereby increasing costs and user difficulty.
Therefore, the air mattress must compromise between providing a uniform supporting force over a large area, and providing the flexibility of numerous deformations like a spring mattress.